diff --git a/src/agents/guardrail.py b/src/agents/guardrail.py
index f8a272b53..758adb28a 100644
--- a/src/agents/guardrail.py
+++ b/src/agents/guardrail.py
@@ -314,7 +314,11 @@ async def my_async_guardrail(...): ...
     def decorator(
         f: _OutputGuardrailFuncSync[TContext_co] | _OutputGuardrailFuncAsync[TContext_co],
     ) -> OutputGuardrail[TContext_co]:
-        return OutputGuardrail(guardrail_function=f, name=name)
+        return OutputGuardrail(
+            guardrail_function=f,
+            # Guardrail name defaults to function name when not specified (None).
+            name=name if name else f.__name__,
+        )
 
     if func is not None:
         # Decorator was used without parentheses